In aerospace hydraulic applications, engine driven pumps are used to provide a high volumetric flow rate of pressurized oil flow to hydraulic systems. Examples of the engine driven pumps include radial piston devices that operate as pumps. Radial piston devices (either pumps or motors) are characterized by a rotor rotatably engaged with a pintle. The rotor has a number of radially oriented cylinders disposed around the rotor and supports a number of pistons in the cylinders.
Engine driven pumps typically operate to receive hydraulic fluid or oil from a reservoir, and suffer substantial pressure loss along the flow path as the hydraulic fluid reaches the pistons in the pumps. Such pressure loss can cause cavitation inside the pump if the pressure of the hydraulic fluid from the reservoir is not sufficiently high. In the aerospace applications, this issue becomes more significant because aircrafts fly at a height where ambient pressure is significantly lower than on the ground. Furthermore, several rotating components, such as a driveshaft, a rotor, and a coupling adapter, and other components, such as a pintle and a driveshaft chamber, also cause a high pressure drop at the pump. Thus, the engine driven pumps are subject to a low inlet pressure of the hydraulic fluid, thereby increasing a chance of cavitation in the pumps. To reduce the problem, the engine driven pumps are typically equipped with a booster pump arranged upstream of the engine driven pumps. The size of the booster pump is typically determined by the pressure loss of the hydraulic fluid between the reservoir and the piston inlets of the engine driven pump.
One of driving factors for the engine driven pumps is to increase a power density, which is defined as a power to weight ratio. A higher power density achieves a higher operating efficiency of hydraulic systems and ensures lower operating costs in aerospace systems. The pressure loss of the hydraulic fluid at a hydraulic system can require a bigger booster pump, thereby decreasing the power density of the system.